Abnormal functional connectivity has been identified in individuals with schizophrenia, major depressive disorder, and bipolar disorder, according to a study published in the Journal of Affective Disorders. These abnormalities include an imbalance between network segregation and integration.
This single-site study included 126 individuals with schizophrenia, 97 with bipolar disorder, 126 with major depressive disorder, and 188 in a healthy control group, all of whom were administered functional magnetic resonance imaging in resting state. The bilateral orbital frontal cortex, as well an additional region in its left orbital frontal cortex reaching the putamen, showed heightened functional connectivity across all 3 disorders.
The primary motor, visual, and auditory cortices all showed decreased functional connectivity, as did the bilateral thalami and right supplemental motor area. Schizophrenia was associated with the highest degree of alterations, followed by bipolar disorder and then by major depressive disorder.
Limitations in this study included a lack of accounting for variables such as medication or clinical and demographic factors. Additionally, local functional connectivity was only examined at rest.
The study researchers conclude that “[these] findings indicate a disrupted balance between network integration and segregation in [schizophrenia], [bipolar disorder], and [major depressive disorder], including over-integration via increased local [functional connectivity] in the [orbital frontal cortex] and diminished segregation of neural processing with the weakening of the local [functional connectivity] in the primary sensory cortices and thalamus. The shared local [functional connectivity] abnormalities across [schizophrenia], [bipolar disorder], and [major depressive disorder] may shed new light on the potential biological mechanisms underlying these disorders.”
Wei Y, Chang M, Womer FY, et al. Local functional connectivity alterations in schizophrenia, bipolar disorder, and major depressive disorder.. J Affect Disord. 2018; ;236:266-273.